[PDFBOX-3572] AES-Decryption with Bouncycastle throws NullPointerException

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.0.0, 2.0.1, 2.0.2, 2.0.3
• Fix Version/s: 2.0.4, 3.0.0 PDFBox
• Component/s: Crypto
• Labels: bouncycastle decrypt nullpointerexception
• Assignee: Tilman Hausherr
• Reporter: Markus Fensterer
• Created: 15/Nov/16 16:06
• Updated: 25/Mar/17 18:12
• Resolved: 16/Nov/16 08:39

Description

Using AES-Encryption with PdfBox and Bouncycastle yields a null pointer. When JCE is used everything works nicely: com.sun.crypt.provider.AESCipher returns an empty byte array for the last 16 bytes of the metadata dictionary. Bouncycastle returns a null reference.

Demo.java

public class Demo {

    public static void main(String[] args) throws IOException, NoSuchAlgorithmException, NoSuchPaddingException {
        String password = "pw";
        String cipherString = "AES/CBC/PKCS5Padding";
        String testFilename = "test.pdf";

        PDDocument document = new PDDocument();
        AccessPermission ap = new AccessPermission();
        ap.setReadOnly();

        StandardProtectionPolicy policy = new StandardProtectionPolicy(password, password, ap);
        policy.setEncryptionKeyLength(128);
        policy.setPreferAES(true);
        document.protect(policy);
        document.getDocumentInformation().setAuthor("author");
        document.save(testFilename);
        document.close();

        // Decryption with SunJCE works
        Cipher cipher = Cipher.getInstance(cipherString);
        System.out.printf("Provider to use for %s decryption: %s\n", cipherString, cipher.getProvider());
        document = PDDocument.load(new File(testFilename), password);

        Security.removeProvider("SunJCE");

        // Decryption with BouncyCastle fails with NPE
        cipher = Cipher.getInstance(cipherString);
        System.out.printf("Provider to use for %s decryption: %s\n", cipherString, cipher.getProvider());
        document = PDDocument.load(new File(testFilename), password);
    }

}

Output with stacktrace

Provider to use for AES/CBC/PKCS5Padding decryption: SunJCE version 1.8
Provider to use for AES/CBC/PKCS5Padding decryption: BC version 1.54
Exception in thread "main" java.lang.NullPointerException
	at java.io.OutputStream.write(OutputStream.java:75)
	at org.apache.pdfbox.pdmodel.encryption.SecurityHandler.encryptDataAESother(SecurityHandler.java:269)
	at org.apache.pdfbox.pdmodel.encryption.SecurityHandler.encryptData(SecurityHandler.java:152)
	at org.apache.pdfbox.pdmodel.encryption.SecurityHandler.decryptString(SecurityHandler.java:532)
	at org.apache.pdfbox.pdmodel.encryption.SecurityHandler.decrypt(SecurityHandler.java:391)
	at org.apache.pdfbox.pdmodel.encryption.SecurityHandler.decryptDictionary(SecurityHandler.java:512)
	at org.apache.pdfbox.pdmodel.encryption.SecurityHandler.decrypt(SecurityHandler.java:399)
	at org.apache.pdfbox.pdfparser.COSParser.parseFileObject(COSParser.java:798)
	at org.apache.pdfbox.pdfparser.COSParser.parseObjectDynamically(COSParser.java:726)
	at org.apache.pdfbox.pdfparser.COSParser.parseObjectDynamically(COSParser.java:657)
	at org.apache.pdfbox.pdfparser.COSParser.parseTrailerValuesDynamically(COSParser.java:2092)
	at org.apache.pdfbox.pdfparser.PDFParser.initialParse(PDFParser.java:201)
	at org.apache.pdfbox.pdfparser.PDFParser.parse(PDFParser.java:249)
	at org.apache.pdfbox.pdmodel.PDDocument.load(PDDocument.java:891)
	at org.apache.pdfbox.pdmodel.PDDocument.load(PDDocument.java:831)

This could possibly be fixed with a null check in the SecurityHandler before writing to the OutputStream.